Since its launch six years ago, Twitter has had a significant influence in the world. Twitter has introduced a world of pithy, 140-character phrases and quotes. It has inspired creative use of shortened words and punctuation marks. It has also demonstrated an instantaneous aspect of communication, with errant Tweets sometimes resulting in an immediate firestorm of reaction. Beyond the more mundane, the “Twitterverse” also played a dramatic role in the Arab Spring, providing protesters a key platform for their revolt against dictatorial regimes.

Who would have thought typing such short messages could be so impactful?

And, as an article in the Wall Street Journal recently pointed out, beyond the use of Twitter by individuals,

even the stodgiest companies have found their way onto Twitter. They have discovered it isn’t just another marketing channel with a funny name, it’s more like a conversation they need to join or risk losing influence over how consumers view them or their brands.

(Twitter…) has become a very public complaint line, and ill-considered tweets or hacked Twitter accounts have caused plenty of embarrassment.

What are the pitfalls – and advantages – to having an active presence on Twitter? Here’s an assessment of three major companies which are utilizing Twitter quite effectively, with some lessons for every business.